Technical Field
The present invention relates to synthetic resins. More specifically, the present invention relates to epoxy-based composite resins that contain aminosilane derivatives and a urethane compound. The resins are suitable for applications such as anticorrosion protective coatings of mild steel.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
The total cost and environmental consequences of the corrosion problems of metal surfaces have become a major challenge to many industries, especially for the gas and oil industry [H. Potgieter, P. A. Olubambi, L. Cornish, C. N. Machio, E. S. M. Sherif, Influence of nickel additions on the corrosion behaviour of low nitrogen 22% Cr series duplex stainless steels, Corrosion Science, 2008, 50, 2572-2579, incorporated herein by reference in its entirety]. Mild steel is used in large tonnages in marine applications, nuclear power and fossil fuel power plants, transportation, chemical processing, petroleum production and refining, pipelines, mining, construction and metal-processing equipment. Mild steels are vulnerable to very high corrosion rates in aggressive solutions and atmospheres due to their limited alloying content, usually less than 2% by weight [Min Qian, Andrew Mcintosh Soutar, Xiu Hui Tan, Xian Ting Zeng and Sudesh L. Wijesinghe, Two-part epoxy-siloxane hybrid corrosion protection coatings for carbon steel, Thin Solid Films, 2009, 517, 5237-5242, incorporated herein by reference in its entirety]. Protective coatings are typically employed to protect the steel surface from corrosion. Chromate-based corrosion inhibitors have been used extensively in corrosion resistant coatings. However, the hexavalent chromium Cr(VI) ingredient is highly carcinogenic and is on the way of being abandoned. Thus, there exists an urgent need for environmental friendly alternatives with high resistance and equivalent or enhanced corrosion protection [C. Chang, C. Wang, C. Wu, S. Liu, F. Mai, Using ToF-SIMS and EIS to evaluate green pretreatment reagent: Corrosion protection of aluminum alloy by silica/zirconium/cerium hybrid coating, J. Appl. Surf. Sci., 2008, 255, 1531-1533, incorporated herein by reference in its entirety].
In the last two decades, the potential of hybrid organic-inorganic sol-gel materials for the replacement of chrome conversion treatments has generated considerable research and public interest [R. Suleiman, M. Mizanurrahman, N. Alfaifi, B. El Ali, R. Akid, Corrosion resistance properties of hybrid organic-inorganic epoxy-amino functionalized polysiloxane based coatings on mild steel in 3.5% NaCl solution, Corrosion Engineering, Science and Technology, 2013, 48, 525-529; R. Suleiman, M. Khaled, H. Wang, J. Gittens, T. Smith, R. Akid, B. El Ali, A. Khalil. A comparison of selected inhibitor doped sol-gel coating systems for the protection of mild steel. Corrosion Engineering, Science and Technology, 2014, 49, 189-196; R. Suleiman, Corrosion Protective Performance of Epoxy-Amino Branched Polydimethylsiloxane Hybrid Coatings on Mild Steel, Anti-Corrosion Methods and Materials, 2014, 61, 423-430; M. Fedel, M. Olivier, M. Poelman, F. Deflorian, S. Rossi, M.-E. Druart, Corrosion protection properties of silane pre-treated powder coated galvanized steel, Progress in Organic Coatings, 2009, 66, 118-128, each incorporated herein by reference in its entirety]. These materials combine the balanced properties of organic polymers (e.g., flexibility, ductility, dielectric) and silica (e.g., high thermal stability, strength, hardness, UV-VIS absorbance), thus having interesting mechanical and barrier properties on metal surfaces [S. K. Poznyak, M. L. Zheludkevich, D. Raps, F. Gammel, K. A. Yasakau, M. G. S. Ferreira, Preparation and corrosion protective properties of nanostructured titania-containing hybrid sol-gel coatings on AA2024, Progress in Organic Coatings, 2008, 62, 226-235; V. Moutarlier, B. Neveu, M. P. Gigandet, Evolution of corrosion protection for sol-gel coatings doped with inorganic inhibitors, Surface and Coatings Technology, 2008, 202, 2052-2058; S. V. Lamaka, M. F. Montemor, A. F. Galio, M. L. Zheludkevich, C. Trindade, L. F. Dick, M. G. S. Ferreira, Novel hybrid sol-gel coatings for corrosion protection of AZ31B magnesium alloy, Electrochim. Acta, 2008, 53, 4773-4783, each incorporated herein by reference in its entirety]. Sol-gel derived organic-inorganic hybrid coatings are mainly produced through the hydrolysis and condensation reaction of organofunctional alkoxysilane precursors. [M. W. Daniels and L. F. Francis, Silane adsorption behavior, microstructure, and properties of glycidoxypropyltrimethoxysilane-modified colloidal silica coatings, J. Colloid. Inter. Sci., 1998, 205, 191-200; M. W. Daniels and L. F. Francis, Effect of Curing Strategies on Porosity in Silane modified Silica Colloidal Coatings, Mater. Res. Proc. Res. Soc., 1999, 576, 313-317, each incorporated herein by reference in its entirety]. They were prepared also by the blending of siloxanes with hydrocarbon-based polymers; more notably epoxy resins [S. H. Cho, S. R. White, P. V. Braun, Room-temperature polydimethylsiloxane-based self-healing polymers, Chem. Mater., 2012, 24, 4209-4214; M. Y. Sho, H. Kwon, Comparison of surface modification with amino terminated polydimethylsiloxane and amino branched polydimethylsiloxane on the corrosion protection of epoxy coating, Corrosion Science, 2009, 51, 650-657, each incorporated herein by reference in its entirety]. The corrosion resistance of these coatings has been attributed to their physical barrier properties, which restrict the penetration of the electrolyte towards the metallic substrate [H. Wang, R. Akid, A room temperature cured sol-gel anticorrosion pretreatment for Al 2024-T3 alloys, Corrosion Science, 2007, 49, 4491-4503, incorporated herein by reference in its entirety]. The chemical structure and organic functionality of silanes can be varied in order to achieve the maximum effect in terms of hydrolytic stability of the interface, desired hydrophobicity or adhesion properties.
Although siliconized epoxy hybrid materials have been reported in the literature, reports on similar materials having urethane moieties are very rare. [D. K. Chattopadhyay, D. C. Webster, Hybrid coatings from novel silane-modified glycidyl carbamate resins and amine crosslinkers, Progress in Organic Coatings, 2009, 66, 73-85; A. J. Vreugdenhil, V. J. Gelling, M. E. Woods, J. R. Schmelz, B. P. Enderson, The role of crosslinkers in epoxy-amine crosslinked silicon sol-gel barrier protection coatings, Thin Solid Films, 2008, 517, 538-543; P. Gupta, M. Bajpai, Development of Siliconized Epoxy Resins and Their Application as Anticorrosive Coatings, Advances in Chemical Engineering and Science, 2011, 1, 133-139; P. Bajpai and M. Bajpai, Development of a high performance hybrid epoxy silicone resin for coatings, Pigment & Resin Technology, 2010. 39, 96-100; S. K. Rath, J. G. Chavan, S. Sasane, Alips Srivastava, M. Patri, A. B. Samui, B. C. Chakraborty, S. N. Sawant, Coatings of PDMS-modified epoxy via urethane linkage: Segmental correlation length, phase morphology, thermomechanical and surface behavior, Progress in Organic Coatings, 2009, 65, 366-374; R. Suleiman, H. Dafalla, B. El Ali, Novel hybrid epoxy silicone materials as efficient anticorrosive coatings for mild steel, RSC Advances, 2015, 5, 39155-39167 each incorporated herein by reference in its entirety].
In view of the foregoing, and as part of the continuing efforts in developing new coating compositions, the present disclosure provides epoxy-based resins that have been functionalized to enhance their corrosion resistance.